leetcode 剑指 Offer 05. 替换空格

地址

replace 和replaceAll

JAVA中 replace没有正则，空格替换需要指定。replaceAll有正则。

s = "We are happy."
System.out.println(s.replaceAll("\\s", "%20")); //We%20are%20happy.
System.out.println(s.replace("\\s","%20"));//We are happy.
System.out.println(s.replace(" ","%20")); // We%20are%20happy.
           

s="   ";
System.out.println(s.replaceAll("\\s", "%20"));//%20%20%20  
System.out.println(s.replaceAll(" ", "%20"));//%20%20%20
System.out.println(s.replace(" ","%20"));//%20%20%20
System.out.println(s.replace("\\s","%20")); // "   "
           

从测试结果看，replace是最优解。

return s.replace(" ","%20");
执行用时: 0 ms
内存消耗: 36.4 MB

return s.replaceAll("\\s", "%20");
执行用时: 2 ms
内存消耗: 36.6 MB

return s.replaceAll(" ", "%20");
执行用时: 3 ms
内存消耗: 36.2 MB
           

不调用API，运行结果没啥差别。

class Solution {
    public String replaceSpace(String s) {
        int len = s.length();
        char[] arr = new char[len*3];
        int p=0;
        for(int i=0;i<len;i++){
            if(s.charAt(i)==' '){
                arr[p++]='%';
                arr[p++]='2';
                arr[p++]='0';
            }else{
                arr[p++]=s.charAt(i);
            }
        }
        return new String(arr,0,p);
    }
}
执行用时: 0 ms
内存消耗: 36.3 MB